In recent years, high quality photographic light-sensitive materials suitable for rapid processing have been desired as a part of improvements in customer services for printing photographic information from digital cameras and as a measure for improving productivity in the photograph treatment service industry. In order to cope with this desire, it is generally carried out, at present, to subject photographic light-sensitive materials containing high-chloride emulsions (hereinafter referred to as high-chloride print materials also) to laser exposure and then to color-development processing (for instance, photographic processing is performed using Frontier 330 Series (trade name) and CP-48S Series Chemical (trade name), made by Fuji Photo Film Co., Ltd.). Further, for example, an exposure treatment system are being put to the market from each company in which system, the process since the exposure step is started until the drying step is finished is rapidly carried out in a total time about 4 minutes by shortening the time required from the exposure to the treatment (called latent image time in the field concerned) to about 10 seconds and carrying out the subsequent color developing treatment for 45 seconds (for example, in Frontier 350 manufactured by Fuji Photo Film Co., Ltd.). An exposure treatment using these systems is carried out in each photo processing shop, and the shop offers its service to return a photographic image to customers in about one hour from reception in these days. These systems are superior in shortening the time required until a photographic image is returned to customers.
With recent improvements in high-chloride print materials and photographic processing technology, the Dry-to-Dry time required to finish one sheet of print has become reduced to the order of 3 to 5 minutes. However, it is still hard to say that the rapidity of such high-chloride print material-utilized rapid processing systems is sufficient as compared with the rapidity of image formation by other color image formation systems (e.g. an electrostatic transfer system, a thermal transfer system, an inkjet system), and therefore it is desired to further reduce the total processing time required for a high-chloride print material to undergo all process steps from the start of development to the end of drying. On the other hand, high-chloride print materials have advantages of high productivity and quality stability over other systems. If it is possible to reduce the Dry-to-Dry time while maintaining high quality, further improvements in productivity can be achieved to result in improvement of profit for minilab print shops that are suffering decreased profitability.
The foregoing exposure-and-processing systems (e.g. a Frontier 350 (trade name)) enable returning of high-quality prints to customers through processes of capturing information from negative images formed by taking pictures, and performing image processing. Further, these systems enable conversion of digital information from image-recording media of digital cameras, which are enjoying an upsurge in their saturation level into laser-beam power and exposure of print materials to laser-beam power. Therefore, customers using services of making photographic prints from digital cameras in photo-developing shops is increasing. In performing print-making from digital cameras, the time required to return prints to each individual customer is determined by the image-capture time and the print-processing time. Accordingly, reducing the print-processing time can directly lead to short-time print service offered for customers, so intensive studies have been conducted on silver halide photographic materials and processing systems that permit faster processing.
Under these circumstances, various studies and efforts to develop methods to improve stability in continuous processing have been made in this industry. To improve productivity and enable rapid processing, it is required to develop (1) high-chloride print materials having rapid processing suitability (and permitting faster color development, faster desilvering, and faster washing), (2) minilabs enabling consistent formation of high image quality prints that are free of unevenness and streaks and have uniform and stable image quality throughout the print from white background to high-density areas, even when the processing speed is increased for processing speed acceleration, and (3) highly activated processing solutions forming neither precipitates nor deposits even when used in continuous processing. Of these developments, development of (1) high-chloride print materials, in particular, can greatly contribute to processing speed acceleration, and therefore intensive study of such materials has continued.
It is well known that images are formed in silver halide color photographic light-sensitive materials by utilizing exposed silver halide as an oxidant, and making an oxidized aromatic primary amine developing agent react with couplers, to produce dyes, such as indophenol, indoaniline, indamine, azomethine, phenoxazine and phenazine dyes. In this photography, a subtractive color process is used, and color images are formed from yellow, magenta and cyan dyes. Of these dye images, cyan dye images are usually formed from phenol- or naphthol-series couplers. However, the dyes formed from those couplers have undesirable absorptions in the yellow-to-magenta region, and have a problem of worsening color reproduction. Therefore, there is a need to solve the problem. Aiming to solve the problem, heterocyclic compounds having particular structures are proposed (e.g., in U.S. Pat. Nos. 4,728,598 and 4,873,183, and European Patent No. 0 249 453 A2), but those couplers each suffer a critical defect, such as low coupling activity or poor colorfastness of the dye formed. As couplers able to overcome such a problem, pyrrolotriazole-series couplers are proposed in U.S. Pat. No. 5,256,526 and European Patent No. 0 545 300. These couplers are outstanding for hue and coupling activity, but the dye images formed from them do not always have sufficient fastness, and their lightfastness, in particular, is inferior to those formed from conventional couplers. As such, there is also a need to overcome such a drawback. In addition, there arises the problem that, when the coupling activity of a coupler is raised by lowering pKa and rapid processing is carried out, a developing agent may be left in print owing to insufficient washing. The developing agent is converted into its oxidation product by air oxidation progresses gradually upon long-term storage of the print, and the oxidation product undergoes coupling reaction with the dissociated coupler in the print to produce a dye as stain. Further, the magenta dyes and the cyan dyes formed have high luminosity factor, such that even slight stains have strong influence on deterioration of white background.
On the other hand, to reduce the time period from reception to completion of printing, even with an accompanying concentrated increase in processing volume, it has been studied to increase the processing volume per unit of time by increasing the conveying speed throughout the processing. To consistently conveying photosensitive materials at increased speed, studies have been made to achieve high-speed conveying by nipping conveying of the photosensitive materials with many pairs of conveying rollers. However, there is apprehension that speeding up conveying may cause an increase in the physical load on photosensitive materials under conveying, to result in sensitivity variation by abrasion in the wet state. More specifically, when photosensitive materials come into contact with unforeseen extraneous substances or protuberances during conveying through processing solutions, and thereby some pressure is applied thereto, it is noted that there occurs a phenomenon in which the photosensitive materials undergo undesirable sensitization or desensitization; as a result, the prints obtained lose commercial value. U.S. Pat. No. 5,543,281 and JP-A-8-254800 (“JP-A” means unexamined published Japanese patent application) disclose the advantage that a photographic element containing silver chloride grains containing a phenyl mercaptotetrazole transition metal salt can reduce cyan stains generated in a developer contaminated by a bleach-fix solution, without causing deterioration in wet abrasion resistance. In addition, JP-A-2002-162707 discloses the art of improving wet abrasion sensitivity by use of a mercapto compound. However, those arts are not always sufficient for wet abrasion sensitivity improvements when photographic materials are conveyed at increased speeds, namely in the case of high-speed conveying. U.S. Pat. Nos. 4,957,855 and 5,320,938 have already disclosed that silver halide emulsions having reduced fog and excellent raw stock can be obtained by use of phenyl mercaptotetrazole and its derivatives. However, these methods have a drawback of exacerbating wet abrasion sensitivity. Under these circumstances, there has been a need to improve wet-state abrasion in the case of high-speed conveying.
In the photograph treatment service industry, color print systems for obtaining color prints from digital cameras, of late, in addition to obtaining them from color negatives and reversal materials, have come into widespread use in not only laboratories specialized in processing of prints but also photo-processing shops. The dominating exposure method adopted in those color print systems is moving from the so-called direct (analog) exposure method that is a method of performing surface exposure of photosensitive materials by being incident projection rays of photographic films such as color negatives on color papers, to a printing system that utilizes digital exposure and enables the making of color prints from digital cameras. A digital exposure method is becoming prevalent even in the case of images recorded on film, wherein the images are read with a photoelectric device, and thereby the information thereof is converted into digital signals; the signals are subjected to image processing, and then scanning exposure for recording images is performed, using recording light modulated in response to the image data obtained by the image processing.
As to the processes for color printing, on the other hand, technologies such as an inkjet process, a sublimation process and color xerography have progressed individually; as a result, these processes have become talked in terms of “Photographic Quality” and these processes are recognized as the processes for color printing. Among these contending technologies, the digital exposure systems using color photographic paper and performing exposure by laser-beam scanning are characterized by high image quality, high productivity, and high fastness of the images formed. Therefore, it is desired to foster enhancements of these characteristics and to provide higher-quality photographs with greater ease at lower prices. To further enhance the image quality in laser scanning exposure of color photographic paper, it is effective to increase the writing density of image data. In addition, speeding up the operations from exposure of color photographic paper to the end of photographic processing enables return of high-quality prints in a short time, on the order of several minutes after the receipt of a recording medium of a digital camera, in a print shop. As a result, the superiority of color prints using color photographic paper is increasingly enhanced. Therefore, it is vitally important that suitability for speeding up the entire process from exposure to the end of photographic processing be imparted to color photographic paper and an image-forming method using the color photographic paper.
Measures to perform the entire process from exposure to the end of photographic processing with rapidity have been examined from various standpoints. Silver halide emulsions used in color photographic paper are silver halide emulsions having high chloride contents, because of their requirement for rapid processing suitability. The development of high-chloride emulsions proceeds at high speed, and produces no development inhibitors such as Br ion and I ion. As a result, there occurs no accumulation of those ions in a developer, and the emulsions are stable to variations in processing factors. JP-A-2002-23295 discloses sensitizing dyes that produce slight residual color, aiming at shortening washing process time. Such speeding up in processing operations results in enhanced print productivity per unit of time, and therefore it is very important.
In those color print systems, photosensitive materials are wound in roll form and loaded in lightproof magazines used for storage of photosensitive materials, and they are drawn from the magazines and conveyed at the occasions of exposure and photographic processing. Hitherto color prints have been made by the so-called roll conveying system; namely, the system in which a photosensitive material undergoes exposure and photographic processing as it is held in roll form without being cut in the progress of processing; and, after completion of the processing, the thus processed photosensitive material is cut to the desired length, to deliver color prints on a sheet-by-sheet basis. This system requires the formation of frame information, to clearly indicate the sheet-by-sheet print boundaries, so it has the drawback that the areas bearing the frame information result in waste, and it has reduced productivity.
In recent years, there has been commercialization of color print systems adopting a sheet conveying method, in which a photosensitive material is cut into sheets of a size equivalent to a photo print sheet in advance, and then is subjected to exposure and photographic processing. In this sheet conveying method, a photosensitive material cut into sheets is conveyed by means of pairs of conveying rollers and a belt conveyor, and undergoes photographic processing. Herein, the photosensitive material in sheet form is development-processed after exposure. In the development-processing step also, the photosensitive material is conveyed by means of pairs of conveying rollers, as it is held in sheet form. Such a color print system is desired to increase the print output number per hour, and preferably such a high-productivity print system can be materialized a comparatively compact apparatus. Under these circumstances, systems that perform photographic processing operations at an ever-faster conveying speed are beginning to displace conventional conveying systems.
However, such increasing of conveying speed requires that photosensitive materials used in those systems, or color paper, have ever-higher suitability for high intensity exposure, photographic processing consistency and rapid processing suitability. To respond to these requirements, improvements in reciprocity characteristics of silver halide emulsions, improvements of couplers and coupler dispersions for ensuring color generation by efficient coupling reaction with oxidized color-developing agents, and improvements added to designs of photosensitive materials in their entirety, including the improvements mentioned above, have been studied in this industry. Although these efforts have been made, further improvements in photosensitive materials and photographic processing systems are desired to further enhance the productivity and handling characteristics required for the color photographic processing systems.
Photosensitive materials used in these systems, or color print materials, are required not to cause a sensitivity drop attributable to high intensity reciprocity law failure. This is because the photosensitive materials used therein, namely color print materials, undergo exposure at high intensity that is responsive to the digital exposure method of recording images by scanning with laser beams modulated by image data. In addition, it is desired that color print materials have consistent finish quality in the sense that they are highly resistant to developer streaks likely to occur in rapid processing under high-speed conveying, and they are less prone to being abraded by contact with guides and blades set in a conveying path through processing solutions.
To ensure favorable physical properties of films in manufacturing color print materials, the color print materials are stored at the factory for a time period of several days from the completion of coating operations to shipment, and the materials shipped from the factory are passed through distribution channels and used in photofinishing laboratories and photo-processing shops. Preferably, the color print materials shipped from the factory are stored at low temperatures, but in fact, often they are left standing in places out of refrigeration; and worse, it often happens, depending on the district, that they are exposed to high temperature or high humidity situations. The method by which the property of hardening with rapidity and the property of raw stock after manufacturing are imparted to color print materials is described, e.g., in JP-A-2000-98527.
Under circumstances in which the variety of color print systems, including systems of a rapid type, has increased, the color print systems of a high-speed sheet conveying type enhanced in productivity are required to deliver high quality equivalent to traditional systems. As things stand now, however, they do not always meet quality requirements to a sufficient degree, specifically regarding the variations in developed color density and gradation, and the incidence of scratches. Further, it turns out that increases in variation of color generation and incidence of scratches occur especially when the storage histories (temperature and humidity) of color print materials after manufacturing are improper.
As stated above, silver halide emulsions used in color photographic paper are silver halide emulsions having high chloride contents, because of their requirement for rapid processing suitability. The development of high-chloride emulsions proceeds at high speed, and produces no development inhibitors such as Br ion and I ion. As a result, there occurs no accumulation of those ions in a developer, and the emulsions are stable to variations in processing factors.
By incorporating various forms of high-bromide phases into high-chloride emulsions, so that the phases are in a localized state, high sensitivities are attained (as described, e.g., in JP-A-2003-207865 and U.S. Pat. Nos. 5,399,475 and 5,284,743). Further, U.S. Pat. Nos. 5,726,005 and 5,736,310 disclose that high-speed emulsions reduced in high intensity failure are obtained by containing iodide so as to have its maximum concentration at the sub-surfaces of high-chloride emulsions. In addition, European Patent No. 0 928 988 A discloses, in its Examples that emulsions having excellent properties with respect to reciprocity raw failure, temperature dependency throughout exposure, and pressure resistance are obtained by incorporating specified compounds into emulsion grains that have I-bands formed at the time when the grain formation reaches 93% of its entire process, and an edge length of 0.218 μm, or a sphere-equivalent diameter of about 0.27 μm.
It is known to dope a silver chloride emulsion with an iridium (Ir) complex, to improve high intensity failure of the emulsion and obtain hard gradation even under high intensity. For instance, JP-B-7-34103 (“JP-B” means examined Japanese patent publication) discloses that the problem of latent-image sensitization is solved by forming localized phases having high silver bromide contents and doping the localized phases with iridium. U.S. Pat. No. 5,691,119 discloses the method of making the gradation in high intensity hard by the method of preparing an emulsion having localized phases high in silver bromide content. In addition, U.S. Pat. No. 5,360,712 discloses cases of improving high intensity failure by use of specified metal complexes having organic ligands.
However, none of those references suggest improvement of streak-form unevenness caused by high-density and high-speed exposure, and by reduction in the time period from exposure to color development.
Further, there has been commercialization of color print systems adopting a sheet conveying method, in which photographic paper is cut into sheets of a size equivalent to a photo print sheet in advance, and then light beams, modulated according to the image data, are deflected to a main scanning direction, and simultaneously therewith, the photographic paper is conveyed in a sub-scanning direction orthogonal to the main scanning direction, and further subjected to photographic processing as it is in sheet form. However, this conveying method has the problem of suffering exposure unevenness, because vibrations are caused by various factors during the conveying and are transferred to an exposed area of photographic paper. For instance, vibrations are transferred to, or load variations occur in, an exposed area of photographic paper by passage of the leading end or the trailing end of the photographic paper over a segment in which a level difference is present between a flatter guide supporting photographic paper in the exposure section and a conveying guide placed at the front of the exposure section, or by an action that the photographic paper takes to get over a conveying roller protruding from the flatter guide level, and thereby, exposure unevenness results.
JP-A-2003-212384, therefore, discloses the image-forming method of good quality by avoiding exposure unevenness from developing, wherein special hard metal rollers, made by adopting metal rollers suffering slight deformation as conveying roller pairs, and by providing rubber layers on the roller surfaces to enhance rollers' conveying performance, are placed so as to protrude their nip positions, and thereby vibrations of photosensitive materials are controlled to result in prevention of exposure unevenness. In this case, a photosensitive material is conducted to an exposure position by means of a pair of conveying rollers and a conveying guide, and it undergoes recording of images in a condition that it is nipped and fixed by pairs of rollers at two points situated in the vicinity of the exposure position so as to face each other across the exposure position, thereby securing the flatness.
In use of the aforementioned hard rollers providing exposure unevenness improvement in the sheet conveying method, however, it turned out that, in some cases, streaked unevenness came to develop in proximity to the points of passage over the hard rollers as the sub-scanning speed under exposure was increased. We have made intensive studies and have conducted tests on a wide variety of photosensitive materials, based on the assumption that the streaked unevenness was pressure sensitization caused by direct damage to emulsions from pressure. As a result thereof, it has been found that the streaked unevenness was not a phenomenon occurring only on the testing level regarded as low in pressure resistance in particular. Further, it has been found that the streaked unevenness developed conspicuously when photosensitive materials stored under circumstances of high temperature and low humidity underwent exposure. Thus, the streaked unevenness has proved to be a phenomenon ascribed to both ageing changes by storage history of photosensitive materials and damage to photosensitive materials under roller conveying.
As stated above, preferably photosensitive materials shipped from the factory are stored at low temperatures, but actually, often they are left standing in places out of refrigeration; and worse, it often happens, depending on the district, that they are exposed to high temperature or high humidity situations. Under circumstances in which color print systems have diversified into rapid types and so on, it is required for high-speed conveying color print systems enhanced in productivity to deliver high quality equivalent to that of color print systems currently in use.
JP-A-2002-23295 discloses that emulsions having excellent pressure resistance can be obtained by spectral sensitization with specified monomethine dyes, but it has no description of changes in photographic properties by variations in ageing of photosensitive materials under storage.
JP-A-2001-166411 discloses that the stability to changes in photographic properties by temperature variations under exposure can be improved by use of specified disulfide compounds, but it also has no description of changes in photographic properties by variations in ageing of photosensitive materials under storage.